Robust increase in South Asian monsoon rainfall under warming driven by extratropical clouds and ocean

Article Open access Yen-Ting Hwang & Jian Lu npj Climate and Atmospheric Science 7 , Article number: 318 (2024) Cite this article Metrics Abstract The responses of South Asian Monsoon (SAM) circulation under global warming are known to be highly uncertain, leading to the widespread of SAM rainfall projections among models. Here, we show that the uncertain SAM circulation in Coupled Model Intercomparison Project Phase 6 models consists of two robust components that partly offset each other: a weakening component linked to a global thermodynamic constraint and a northward shift component understood through a regional 2D energetic perspective. We further attribute the robust northward shift of SAM circulation to positive cloud feedback over the Eurasia Continent and heat uptake in the Southern Ocean. A set of climate model simulations supports the finding that SAM rainfall increase is primarily due to the northward shift of circulation driven by extratropical processes. This energetic perspective opens new avenues for predicting monsoon rainfall by connecting circulation changes to radiative forcing, feedbacks, and ocean heat uptake. Introduction The South Asian summer monsoon (SAM) rainfall has important impacts on agriculture and economy 1 . Understanding its responses to global warming is critical to future projections; however, a significant spread exists among the projected changes of SAM rainfall in climate models 2 , 3 , 4 . Moreover, the observational records are largely influenced by aerosol effects and decadal natural variability 5 , 6 , 7 , 8 , 9 , 10 , 11 , making it even harder to constrain the diverging future projections in climate models. In many previous studies and the most recent report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), the responses of SAM rainfall to global warming are often understood by partitioning into the thermodynamic and dynamic components 4 […]

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